Ammonia production and amino acid metabolism by rat renal papillary epithelial cells in culture

B. L. Margolis, M. D. Lifschitz

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

A significant percentage of excreted ammonium is added to tubular fluid along the medullary collecting duct. However, it is not clear whether this ammonia is produced in the cortex and delivered into the medulla or is produced directly by medullary cells. To address this issue, rat epithelial cells derived from the renal papilla were grown in continuous culture and their ability to generate ammonia was examined. When grown in Dulbecco's modified Eagle's medium with a 4 mM glutamine, these cells produced ammonia at a rate of approximately 27 nmol/106 cells/h. When these cells were grown in minimum essential medium without glutamine, ammonia production fell to 7 nmol/106 cells/h. Increasing the glutamine concentrations of minimum essential medium to 4 mM increased ammonia production to slightly greater than 30 nmol/106 cells/h. Increasing the media concentration of glutamate, glycine, or asparagine resulted in no significant increase in ammoniagenesis. Analysis of media amino acid concentration revealed that glutamine was the main amino acid consumed while alanine was the predominant amino acid produced. The glutaminase activity of these cells appears to be primarily phosphate-dependent, similar to that observed in vitro in papillary tubules. Alterations of K+ or H+ ion concentration did not alter ammoniagenesis, but addition of 2.5 mM ammonium chloride significantly reduced net ammonia production. It is concluded that rat papillary epithelial cells have the intrinsic ability to utilize glutamine to generate ammonia and alanine. In vivo ammonia produced locally in the medulla may contribute to final urinary ammonium excretion.

Original languageEnglish (US)
Pages (from-to)501-507
Number of pages7
JournalJournal of Biological Chemistry
Volume260
Issue number1
StatePublished - 1985

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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